Two men of mass 60 kg and 80 kg stand on a plank of mass 20 kg . Both of them can jump with a velocity of 1 m / s relative to the plank. In each event shown in List-I, find the velocity of plank after

Question

Two men of mass 60 kg and 80 kg stand on a plank of mass 20 kg . Both of them can jump with a velocity of $1 m / s$ relative to the plank. In each event shown in List-I, find the velocity of plank after the event. Sign of right direction is (+ve) and (-ve) for left direction.

List - I	List - II
(I) Ram alone jumps to the left	(P) $- \frac{17}{40} m / s$
(II) Shyam alone jumps to the right	(Q) $- \frac{1}{2} m / s$
(III) Ram jumps to left and Shyam jumps to right simultaneously	(R) $\frac{3}{8} m / s$
(IV) Ram jumps to left and after that Shyam jumps to right.	(S) $- \frac{1}{8} m / s$
	(T) $\frac{1}{3} m / s$

TestHub · Accepted Answer

(I) P i ​ = P f ​ ⇒ 60 ( 1 − V ) = 100 V ⇒ V = 8 3 ​ opposite to velocity of Ram i.e. 8 3 ​ m / s towards right. (II) 80 V = 80 ( 1 − V ) ⇒ V = 2 1 ​ m / sec left. (III) 80 ( 1 + V ) + 60 ( − 1 + V ) + 20 V = 0 V = − 8 1 ​ m / s (IV) After jump of Ram 80 → 3/8 Now ( 80 + 20 ) 8 3 ​ = 80 ( 1 + V ) + 20 V ⇒ V = − 40 17 ​ m / s

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JEE Main + Advanced (1 year 12th class)

JEE Advanced (2028)